1. Field of the Invention
The present invention relates to power sensor circuits and, in particular, to power sensor circuits for use with digital convergence systems used with cathode-ray tubes.
2. Description of the Related Art
Electrical components such as integrated circuits (ICs) and amplifiers are commonly coupled to power supply devices that provide various supply voltages to the components. When a power supply device fails for some reason, the electrical components receiving supply voltages from the power supply are invariably affected, which can lead to undesired results, depending on the nature of the electrical components.
For example, in television (TV) systems such as projection TV cathode ray tube (CRT) systems, there are typically three CRT units, one for each of the colors red, green, and blue. In order to correct a display artifact known as vertical pincushion distortion, a convergence system is utilized to provide a convergence correction wave form or signal to each of the red, blue, and green CRT units. These convergence correction signals correct for the vertical pincushion distortion effect and other distortions, thereby helping to maintain a linear, nondistorted picture on the screen of each CRT. Typically, the convergence system contains a digital convergence IC, a pre-amplifier (preamp), and a power amplifier (power amp). The digital convergence IC generates the correction signal, typically a current, which is applied to the preamp for signal conditioning and differential amplification. The preamp provides an output voltage which is applied to the power amp for power amplification before coupling to a convergence yoke coil. The preamp typically contains one or more operational amplifiers (op amps).
The digital convergence IC, as well as the preamp and the power amp, require various supply voltages to function properly. For example, the digital convergence IC may require a +5V input voltage, and the preamp and power amp may require both +15V and -15V power supply voltages. If, for some reason, the +5V input to the digital convergence IC is disturbed while the IC is providing the correction signal to the preamp, undesired effects may occur. For example, the digital convergence IC may generate inappropriate waveforms, which could damage or destroy the power amp, since the power amp is inductively loaded and produces excessive heat with improper signals (such as signals with DC components).
Additionally, if either of the +15V or -15V power supply voltages are disturbed while the IC is powered by the +5V input and is providing the correction signal to the preamp, undesired effects may cause the preamp or power amp to generate inappropriate amplified signals, which could damage or destroy the power amp or other components of the convergence system.